The practicability of using a substoichiometric mixture of air and methane to feed the anode compartment of a solid oxide electrochemical reactor has been tested at laboratory level through the operation of a 150W tubular stack. Fuel is partially oxidized to synthesis gas as an alternative to steam reforming of natural gas in solid oxide fuel cells. A simulation model of the electrochemical reactor, including mass, heat and charge balances is presented. Experimental results confirm the simulation ones and the model gives new insights into the phenomenological behaviour of the whole process.